How to set/reset the start date to today using new request parameters with non-obsolete definition

How to set/reset the start date to today using new request parameters with non-obsolete definition.

I tried giving the valuation script as Dim today As DateTime = DateTime.Now
value = today

and validation script as Dim today As DateTime = DateTime.Now
If Provider.GetValue(Of Date)("Startdate") <> today Then
value = today
end if

but this is not working, can anyone guide?